1. Field of the Invention
The present invention relates to an automotive rotary electric machine having permanent magnets disposed between claw-shaped magnetic pole portions of a rotor, and particularly to a permanent magnet shape relative to a claw-shaped magnetic pole shape in order to achieve improvements in various characteristics.
2. Description of the Related Art
In conventional automotive rotary electric machines, an outer peripheral surface shape of claw-shaped magnetic pole portions of a rotor core is formed so as to have a trapezoidal shape constituted by a tip end short side, a base end portion long side, and two oblique sides, permanent magnets being disposed between the claw-shaped magnetic pole portions. With objectives of preventing battery overcharge and of achieving high efficiency and high output, the claw-shaped magnetic pole portions and the permanent magnets are constructed so as to satisfy 0.2≦Br{L/(W cos θ)}≦0.8, where Br is a residual magnetic flux density of the permanent magnets, L is a magnetic pole portion length from the tip end short side of the claw-shaped magnetic pole portions to the base end portion long side, W is a length of the base end portion long side of the claw-shaped magnetic pole portions, and 2θ is an angle formed by the two oblique sides of the claw-shaped magnetic pole portions. (See Patent Literature 1, for example.)
Patent Literature 1: Japanese Patent No. 2990810 (Gazette)
In conventional automotive rotary electric machines, since no consideration has been given to ineffective magnetic flux generated when magnetic flux flowing through the rotor core is saturated at the base end portions of the claw-shaped magnetic pole portions, magnetic flux arising due to field current flowing through the field winding has not been utilized effectively.
Because the permanent magnets disposed between the claw-shaped magnetic pole portions are formed so as to have a rectangular shape in which a circumferential side surface shape has a length from the tip end short side of the claw-shaped magnetic pole portions to the base end portion long side as a long side and a base end portion radial length of the claw-shaped magnetic pole portions as a short side, additional magnetic flux from the permanent magnets has not been used efficiently since a portion of the circumferential side surface of the permanent magnets does not come into contact with the circumferential side surface of the claw-shaped magnetic pole portions on an inner radial side.